1. Field of Invention
The invention relates to ceramics and methods of production and, in particular, to C-plane single crystal sapphire and methods of making C-plane single crystal sapphire.
2. Discussion of Related Art
Single crystal sapphire, or α-alumina, is a ceramic material having properties that make it attractive for use in a number of fields. For example, single crystal sapphire is hard, transparent and heat resistant, making it useful in, for example, optical, electronic, armor and crystal growth applications. Due to the crystalline structure of single crystal sapphire, sapphire sheets may be formed in various planar orientations including C-plane, m-plane, r-plane and a-plane. C-plane single crystal sapphire has homogeneous properties that may provide advantages over other orientations. One application where C-plane sapphire may be preferred is in the field of optics where, for instance, the absence of natural crystallographic birefringence may be advantageous. Other applications include those where faster material removal from the sapphire surface is desired. C-plane sapphire may also be useful in the growth of LEDs, such as, for example, gallium nitride LEDs.
Several techniques for the production of single crystal sapphire are known including the Kyropolos, Czochralski, Horizontal Bridgman, Verneuile technique, heat exchange, and shaped crystal growth techniques such as edge defined film-fed growth methods.